The present invention relates to a lock mechanism for a limiting contact maker, of the kind comprising at least one set of switches which can be closed and opened by a control electromagnet, which forms its contact making function, or else opened only by a device which, associated with an overload detector, provides rapid opening corresponding to the limiting function.
The limiting function has priority over the contact making function, which means that in the case of closure on a short circuit, the process of opening the switches must take place as rapidly as possible. For this, the control for opening the switches is provided by an appropriate mechanism, cut-off of the power supply to the electromagnet only taking place so as to confirm the cutoff.